Articular cartilage injuries affect approximately 900,000 individuals in the United States every year. Numerous surgical interventions exist which focus on inciting cartilage repair including debridement and chondroplasty, microfracture, osteochondral allograft transplantation, and autologous chondrocyte implantation (ACI). These techniques have varying levels of success, with the ultimate goal being to generate hyaline cartilage in the defect, to recreate normal articular congruity, and to improve overall functioning, disability and health. Of these various techniques, microfracture is the most commonly utilized.
The microfracture procedure is a form of bone-marrow stimulation which enhances cartilage repair by taking advantage of the body's own healing potential. A sharp awl (i.e., a pick) is used arthroscopically through one of the arthroscopic skin portals and a mallet is used to impact the awl into the subchondral bone and thus generate bleeding from the bone. Holes are created at regular intervals until the entire defect has been addressed. The penetration of the subchondral bone allows for the communication of the osteochondral defect with mesenchymal stem cells and growth factors from the bone marrow and eventually leads to the formation of fibrocartilagenous tissue that covers the cartilage lesion.
Microfracture is typically performed by arthroscopy, after the joint is cleaned of calcified cartilage. Through use of an awl, the surgeon creates tiny fractures in the subchondral bone plate. Blood and bone marrow (which contains stem cells) seep out of the fractures, creating a blood clot over the defect. The stem cells from the bone marrow and from the underlying subchondral bone interact with the clot and use this as the initial scaffold to begin the process of cellular differentiation into fibrocartilage or cartilage-building cells. The microfractures are treated as an injury by the body, which is why the surgery results in new, replacement tissue. The procedure is effective in gaining a combination of fibrocartilage and hyaline cartilage (which are not formed from an osteochondritis dissecan (OC) defect alone).
Although good results have been achieved with microfracture treatments, some studies have concluded that, while microfracture provides effective short-term functional improvement of knee function, there is insufficient data on its long-term results. Additional shortcomings of the technique include limited hyaline repair tissue, variable repair cartilage volume, and possible functional deterioration over time.
A recent technology used to augment the microfracture technique is through the use of an allograft extracellular matrix. BioCartilage® is an example of desiccated micronized cartilage extracellular matrix tissue allograft that has been developed for ICRS grade III or greater articular cartilage lesions in conjunction with microfracture.
BioCartilage® is developed from allograft cartilage that has been dehydrated and micronized. BioCartilage® contains the extracellular matrix that is native to articular cartilage including key components such as type II collagen, proteoglycans, and additional cartilaginous growth factors. The principle of BioCartilage® is to serve as a scaffold over a microfractured defect providing a tissue network that can potentially signal autologous cellular interactions and improve the degree and quality of tissue healing within a properly prepared articular cartilage defect.
This allograft tissue is combined with platelet-rich plasma and the resultant solution is added to a microfractured chondral lesion and “fixed” with a fibrin coverage. The addition of platelet-rich plasma (PRP) to the dessicated BioCartilage® scaffold is considered a beneficial addition due to the anabolic and anti-inflammatory factors associated with PRP. The added fibrin content in PRP provides additional structure to the final matrix pre and post implantation.
A need exists for techniques that allow delivery of allograft cartilage tissue over a cartilage defect that has been debrided and microfractured, without the need for a periosteal covering or separate type of patch sewn over the top. Also needed are methods and special delivery instruments for rebuilding a defective cartilage in difficult-to-reach areas such as the ankle. An augmented microfracture procedure that addresses sub-chondral lesions is also needed.